The present invention relates to a plate heat exchanger for exchanging heat between two fluids flowing alternately through adjacent fluid passages between piled plates, and more particularly to a plate heat exchanger suitable for such cases where at least one of the fluids is a low-pressure vapor (or is evaporated with phase change, or is condensed from a vapor), as an evaporator, a low-temperature regenerator, or a condenser in a refrigerating machine using a low-pressure refrigerant.
FIG. 14 shows a configurational example of an absorber and an evaporator utilizing a conventional plate heat exchanger.
Generally, if a flow velocity of a vapor at an outlet of an evaporator or a flow velocity of a vapor at an inlet of an absorber is not suppressed to about 50 m/s or lower, then flow resistance is increased to lower the performance of a refrigerating machine.
In the conventional example, an evaporator 21 and an absorber 22 are disposed on the left side and the right side, respectively. The size of a passage for vapor with respect to four surfaces of the plates appears as
the height of the platexc3x97a gap between the plates/2
Thus, a considerably large gap is required between the plates, and hence it is difficult to achieve compactness. In FIG. 14, the reference numeral 11 denotes cold water, the reference numeral 12 cooling water, the reference numeral 13 a refrigerant liquid, and the reference numeral 14 an absorption solution.
In order to solve this problem, as shown in FIG. 15, there has been proposed a plate heat exchanger in which absorber elements 2xe2x80x2 and evaporator elements 2 are alternately disposed in such a manner that adjacent plate surfaces of the elements are opposed to each other. In this case, the size of a passage for vapor with respect to four surfaces of the plates appears as
the height of the platexc3x97the width of the plate Therefore, the gap between the plates can be designed without the influence of the flow velocity of the vapor, for thereby achieving compactness.
With such a type of heat exchanger as shown in FIG. 15, it is necessary to combine two plates into a heat exchange element, one by one, and then to attach each of the heat exchange elements to a header for cold water and a header for cooling water, one by one. Thus, many man-hours are needed to manufacture the heat exchanger. In this example, the heat exchange element and the header for cold water (or the header for cooling water) are prepared as separate components. Therefore, in the case of 100 heat exchange elements, it is necessary to bond the heat exchange elements to the header at 200 points for the inlets and the outlets. Further, the absorber and the evaporator are different in shape, so that many types of components are required.
Furthermore, in the case where the absorber elements and the evaporator elements are alternately disposed, for example, the absorption solution 14 and the refrigerant liquid 13 simultaneously flow downwardly through the gap between the elements, with scattering droplets thereof. If the absorption solution is mixed into the refrigerant, then the contamination of the refrigerant causes elevation of boiling point to rise the evaporating temperature, thereby deteriorating the performance of the refrigerating machine. Further, the amount of the solution on the heat transfer surface is reduced, so that the heat transfer surface is difficult to be wet.
On the other hand, if the refrigerant liquid is scattered as droplets from the heat transfer surface of the evaporator and introduced into the absorber, then the concentration of the solution is decreased to lower the absorbing ability of the solution, thereby deteriorating the performance of the refrigerating machine. Further, when the refrigerant liquid jumps out in liquid phase without evaporating, the refrigerating machine cannot obtain the inherent refrigerating effect, resulting in lowered efficiency. Further, the amount of the refrigerant liquid on the heat transfer surface is reduced, so that the heat transfer surface is difficult to be wet.
The present invention has been made in view of the above prior art. It is an object of the present invention to provide a plate heat exchanger which can be manufactured at reduced cost of production and assembly from a small number of components, can prevent a droplet from being scattered during supply of a liquid between heat exchange elements, and can flow the liquid on a plate evenly to obtain high efficiency of heat exchanging performance.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a plate heat exchanger for simultaneously exchanging heat between two sets of fluids having different temperatures, characterized in that: the plate heat exchanger comprises: a heat exchange element (A) comprising two plates facing each other as a set so as to form a sealed inner space therebetween as a passage for a first fluid, wherein a plate surface of the plate serves as a heat transfer surface, and a fluid flowing along an outer surface of the plate is a second fluid; and a heat exchange element (B) comprising two plates facing each other as a set so as to form a sealed inner space as a passage for a third fluid, wherein a plate surface of the plate serves as a heat transfer surface, and a fluid flowing along an outer surface of the plate is a fourth fluid; a plurality of the heat exchange elements (A) and a plurality of the heat exchange elements (B) are alternately disposed in such a manner that the plate surfaces of the plates are opposed to each other and a predetermined gap is formed between adjacent the heat exchange elements; and a communication pipe communicating with the inner spaces of the heat exchange elements (A) and a communication pipe communicating with the inner spaces of the heat exchange elements (B) are formed on the plate surfaces of the heat exchange elements (A) and (B) and integrally formed with the elements.
In the plate heat exchanger, the communication pipe communicating with the elements may be constituted by a part of the plate in the element. The two elements (A) and (B) alternately disposed may have the same shapes that are symmetrical in the opposite direction.
In the plate heat exchanger, the first fluid may be cooling water, the second fluid may be an absorption solution, the third fluid may be cold water, and the fourth fluid may be a refrigerant liquid to constitute a plate-type absorber and a plate-type evaporator for an absorption refrigerating machine. Further, the first fluid may be a heat source fluid (such as hot water or vapor), the second fluid may be an absorption solution, the third fluid may be cooling water, and the fourth fluid may be a refrigerant condensate to constitute a plate-type regenerator and a plate-type condenser for an absorption refrigerating machine. Furthermore, the plate-type absorber and evaporator and/or the plate-type regenerator and condenser may be used as an absorber, an evaporator, a regenerator, and a condenser in an absorption refrigerating machine to constitute an absorption refrigerating machine.
According to a second aspect of the present invention, there is provided a plate heat exchanger for simultaneously exchanging heat between two sets of fluids having different temperatures, characterized in that: the plate heat exchanger comprises: a heat exchange element (A) comprising two plates facing each other as a set so as to form a sealed inner space therebetween as a passage for a first fluid, wherein a plate surface of the plate serves as a heat transfer surface, and a fluid flowing along an outer surface of the plate is a second fluid; and a heat exchange element (B) comprising two plates facing each other as a set so as to form a sealed inner space as a passage for a third fluid, wherein a plate surface of the plate serves as a heat transfer surface, and a fluid flowing along an outer surface of the plate is a fourth fluid; a plurality of the heat exchange elements (A) and a plurality of the heat exchange elements (B) are alternately disposed in such a manner that the plate surfaces of the plates are opposed to each other and a predetermined gap is formed between adjacent the heat exchange elements; and scatter preventive means for preventing a droplet from being scattered is provided in the gap.
Preferably, in the plate heat exchanger, a communication pipe communicating with the inner spaces of the heat exchange elements (A) and a communication pipe communicating with the inner spaces of the heat exchange elements (B) are formed on the plate surfaces of the heat exchange elements (A) and (B). Further, the scatter preventive means may be constituted by two plates so as to return a scattered liquid to the heat transfer surface on which the liquid has been scattered.
Further, in the plate heat exchanger of the present invention, the communication pipe communicating with the elements may be constituted by a part of the plate in the elements. The two heat exchange elements (A) and (B) alternately disposed may have the same shapes that are symmetrical in the opposite direction. Furthermore, a liquid distributor for the second fluid and/or the fourth fluid may be disposed on the outer surface of the plate in the heat exchange element (A) and/or the heat exchange element (B).
According to a third aspect of the present invention, there is provided a plate heat exchanger for simultaneously exchanging heat between two sets of fluids having different temperatures, characterized in that: the plate heat exchanger comprises: a heat exchange element (A) comprising two plates facing each other as a set so as to form a sealed inner space therebetween as a passage for a first fluid, wherein a plate surface of the plate serves as a heat transfer surface, and a fluid flowing along an outer surface of the plate is a second fluid; and a heat exchange element (B) comprising two plates facing each other as a set so as to form a sealed inner space as a passage for a third fluid, wherein a plate surface of the plate serves as a heat transfer surface, and a fluid flowing along an outer surface of the plate is a fourth fluid; a plurality of the heat exchange elements (A) and a plurality of the heat exchange elements (B) are alternately disposed in such a manner that the plate surfaces of the plates are opposed to each other and a predetermined gap is formed between adjacent the heat exchange elements; and a liquid distributor for flowing the second fluid and the fourth fluid onto upper portions of surfaces of the heat exchange elements (A) and (B) is provided in the gap.
In the plate heat exchanger, a gutter having an orifice hole in a side surface thereof may be used as the liquid distributor. Further, the liquid distributor may be in the form of a gutter, and the plate surface may be utilized as a side surface of the gutter.
Preferably, a communication pipe communicating with the inner spaces of the heat exchange elements (A) and a communication pipe communicating with the inner spaces of the heat exchange elements (B) are formed on the plate surfaces of the heat exchange elements (A) and (B).